Ann. Zool. Fennici 52: 368–376 ISSN 0003-455X (print), ISSN 1797-2450 (online) Helsinki 18 December 2015 © Finnish Zoological and Botanical Publishing Board 2015 Inter-specific differences in the structure and mechanics but not the chemical composition of antlers in three deer species Francisco Ceacero1,2,*, Jan Pluháček2,3, Tomás Landete-Castillejos4,5,6, Andrés J. García4,5,6 & Laureano Gallego4,5,6 1) Department of Animal Science and Food Processing, Faculty of Tropical AgriSciences, Czech University of Life Sciences, Kamýcká 129, CZ-165 00, Prague 6 — Suchdol, Czech Republic (*corresponding author’s e-mail: [email protected]) 2) Department of Ethology. Institute of Animal Science, Přátelství 815, CZ-104 01 Prague — Uhříněves, Czech Republic 3) Ostrava Zoo, Michálkovická 197, CZ-710 00 Ostrava, Czech Republic 4) Sección de Recursos Cinegéticos y Ganaderos, Instituto de Desarrollo Regional (IDR), Universidad de Castilla-La Mancha (UCLM), ES-02071 Albacete, Spain 5) Instituto de Investigación en Recursos Cinegéticos (IREC), Consejo Superior de Investigaciones Científicas, Universidad de Castilla-La Mancha, Junta de Comunidades de Castilla-La Mancha (CSIC-UCLM-JCCM), Ronda de Toledo s/n, ES-13071 Ciudad Real, Spain 6) Departamento de Ciencia y Tecnología Agroforestal y Genética, ETSIA, Universidad de Castilla-La Mancha (UCLM), ES-02071 Albacete, Spain Received 5 Apr. 2015, final version received 30 June 2015, accepted 14 Aug. 2015 Ceacero, F., Pluháček, J., Landete-Castillejos, T., García, A. J. & Gallego, L. 2015: Inter-specific differences in the structure and mechanics but not the chemical composition of antlers in three deer species. — Ann. Zool. Fennici 52: 368–376. Antlers are costly structures produced annually by male cervids using minerals obtained from their diet and from resorption of their skeleton. Availability and nutri- tive quality of food resources therefore have a great impact on the investment of males in these secondary sexual traits. We studied the structure, mineral composition and mechanical quality of antlers of the Siberian wapiti (Cervus canadensis sibiricus), Père David’s deer (Elaphurus davidianus) and Vietnamese sika deer (Cervus nippon pseudaxis), three closely-related cervid species. The three herds investigated were maintained under the same feeding and management conditions (one male per herd) throughout a 3-year study period. We showed that there was no significant inter-spe- cific difference in antler composition of the three species under the same feeding regime. However, mechanical properties varied between the Siberian wapiti and the other two species; and structural characteristics were different among all of them. Our results show that antler composition has a similar chemical profile across species when grown under the same feeding regime whereas the internal structure and mechanical properties appear to be species dependent. ANN. ZOOL. FENNICI Vol. 52 • Interspecific differences in antler properties 369 Introduction lated cervid species (Hernandez-Fernandez & Vrba 2005) kept captive in Ostrava Zoo (Czech According to prevailing theories on costly sec- Republic): Siberian wapiti or Altai maral ondary sexual characteristics, such as antlers, (Cervus canadensis sibiricus), Vietnamese these structures are believed to indicate quality of sika deer (Cervus nippon pseudaxis), and Père the male, and thus are likely to reflect body con- David’s deer (Elaphurus davidianus). The zoo dition and food intake (Harvey & Bradbury 1991; is located in a large forested area in the center in deer antlers: Ditchkoff et al. 2001, Weladji et of the city. Each species was kept all year round al. 2005). The rate of mineralization of antlers is in outdoor enclosures of the following sizes: faster than in any other animal tissue (Wolfe 1982, 2200 m2 for Vietnamese sika deer, 3000 m2 for Gómez et al. 2013). Antlers are cast every year, Père David’s deer, and 4800 m2 for Siberian even if they constitute up to an astonishing 35% wapiti. Siberian wapiti were introduced to the of the skeleton weight of adult red deer (Cervus zoo in 1961 when one male and two females elaphus: 24% mean value; Gómez et al. 2012). were imported from the Soviet Union. A pair of Two important findings are common to a series Père David’s deer was brought in from Leipzig of recent studies on red deer. First, antler charac- Zoo (Germany) in 1974; and one male and three teristics reflect the physiological effort invested females of Vietnamese sika deer were introduced in their growth. There are differences between from Kronberg Zoo and Tierpark Berlin (both in the top and burr in cortical thickness, chemical Germany) in 1993. Since the establishment of composition (Landete-Castillejos et al. 2007a, the herds, all three species have bred regularly 2007b), mechanical properties (Landete-Castille- and most of the calves have been exported to jos et al. 2007c), and even in histological parame- other holders. During the period of this research ters such as porosity and structure (Landete-Cas- (2010–2012), each of the three herds was com- tillejos et al. 2013). Second, antler characteris- posed of one breeding male (the same males tics vary between deer populations differing in throughout the study period), three to five hinds nutrition and management, with the chemical and their calves. The herds were kept under sim- composition of the antler reflecting that of diet ilar conditions during the study period, including (Landete-Castillejos et al. 2007b, 2013, Estevez having a similar diet based on grass (summer) et al. 2009). This also affects both mechanical and hay (winter), both available ad libitum. Each properties and histology (Landete-Castillejos et animal also received 1.2 kg (Siberian wapiti al. 2007b, 2013). However, few studies that have and Père David’s deer) or 0.4 kg (Vietnamese compared these properties and the relationships sika deer) of pellets per day (see composition in between deer species (Kitchener 1991, Blob & Table 1), and the same amount of oats. During LaBarbera 2001, Pathak et al. 2001, Blob & Snel- winter, 2 kg (Siberian wapiti and Père David’s grove 2006) have produced unclear results, most deer) or 0.5 kg (Vietnamese sika deer) of beet probably due to the antlers being of very different was additionally provided daily per animal. At origins. Thus, it is yet to be discerned if, under least two feeders for hay were available in each the same feeding regime, different species grow enclosure, and the number of feeders for pellets antlers with similar internal structure, chemical and oats matched the number of adult animals composition and mechanical properties. The aim so no adult individual had limited access to food of this study was therefore to compare the antler (Ceacero et al. 2012). One pure-salt block was characteristics of three deer species reared under also always present in each enclosure. The keep- similar nutritional and housing conditions. ers remained the same during the study period. Previous studies have shown that numer- ous factors affect antler growth and properties Material and methods (reviewed by Landete-Castillejos et al. 2012). For our comparative study it was necessary to Collection of samples have similar conditions throughout the study (e.g. stable social environment, housing con- We collected antlers from three closely-re- ditions and feeding regimes, same adult male, 370 Ceacero et al. • ANN. ZOOL. FENNICI Vol. 52 Fig. 1. Scheme of the studied material. Sample levels from the proximal, middle and distal por- tions of the antler in the three species: (a) Cervus canadensis sibiricus, (b) Elaphurus davidianus and (c) Cervus nippon pseu- daxis. same locality, lack of diseases, etc.). As a result tical bone expressed as a percentage (CBA%). of these requirements, size was limited but com- CBT, CBD% and CBA% were used as measures parable data necessary for such a study could be to define bone structure of the antler. gathered. From each sampling level, two rectangular bars of pure cortical bone (50 ¥ 2.5 ¥ 4 mm) were extracted from the internal side and lon- Analytical procedures gitudinal axis of the antler and prepared for mechanical testing. Each piece was initially cut Antlers grown during each of the studied seasons longitudinally into 60 mm long, 4 mm deep and were collected after casting and sampled at three 5 mm wide strips using a low-speed petrographic positions (proximal, middle and distal portions; saw and then polished with no. 400 and 1000 Fig. 1): 6-cm-long cross-sectional pieces were cut from each level. The slices were colored with a 1:4 ink:water solution (Pelikan ink 4001, Ger- Table 1. Composition of pellets (as dry matter) provided to deer during the three-year study period. many) and dried for 24 h at room temperature (Bubenik 1990). The slices were then polished Nutrient Content to increase the contrast between the cortical and Crude protein (%) 15.6 trabecular bones. Finally, the basal transverse –1 cross-sections were scanned (HP ScanJet 4370 lysin (g kg ) 6.9 methionin (g kg–1) 2.3 Photo Scanner) at 400 dpi. The following macro- Crude fat (%) 2.8 scopic variables were measured with the ImageJ Crude fibre (%) 12.7 (National Institute of Health, USA) image anal- Ash (%) 8.7 –1 calcium (Ca, g kg ) 6.7 ysis software: (1) cortical bone thickness (CBT) –1 of the cross-sections (the mean value of six sodium (Na, g kg ) 1.7 potassium (K, g kg–1) 1.0 equally spaced measurements); (2) total diame- phosphorus (P, g kg–1) 4.6 ter (the mean of three equally spaced measure- iron (Fe, mg kg–1) 185.0 ments); (3) proportion of the diameter occupied zinc (Zn, mg kg–1) 110.0 –1 manganese (Mn, mg kg ) 87.0 by the cortical bone (CBD%; calculated from the –1 previous two measurements); (4) total area of the copper (Cu, mg kg ) 14.0 selenium (Se, mg kg–1) 0.31 cross-section; and (5) area occupied by the cor- ANN.